Speakers, as sounding devices of such electronic products as mobile phones, televisions and computers, are widely used in people's daily production and life. Nowadays, there are some common speakers mainly including moving-coil speakers, magnetic speakers, capacitive speakers, piezoelectric speakers, etc.. The moving-coil speakers have the characteristics of relatively simple manufacture, low cost, low-frequency sounding advantage, etc.
The conventional moving-coil speaker, also known as a moving-coil speaker module, usually comprises a speaker module housing and a speaker unit. The speaker module housing typically comprises an upper housing and a lower housing which are assembled together to form a cavity to accommodate the speaker unit. The speaker unit typically comprises a vibration system, a magnetic circuit system and an auxiliary system. The above-mentioned auxiliary system comprises a housing which may accommodate the vibration system and the magnetic circuit system. The above-mentioned vibration system comprises a vibration diaphragm and a vibrating voice coil secured to one side of the vibration diaphragm. The vibration diaphragm comprises a vibration diaphragm body and a DOME (spherical top) secured to the center of the vibration diaphragm body. The vibration diaphragm body comprises a fixed portion secured to the housing, a concave or convex edge portion integrated with the fixed portion and a planar portion located in the edge portion. The magnetic circuit system comprises a frame, a magnet and a washer secured to the frame. The auxiliary system comprises the housing.
With higher and higher demands on the acoustic performance of the moving-coil speaker from people, a technology employing capacitance to feed back vibration displacement of the vibration diaphragm of the speaker unit is applied extensively. Particularly, in this technology, there is a need to dispose a steel sheet on the upper housing of the speaker module housing to serve as an upper electrode plate of a capacitor, and to dispose another steel sheet on the DOME of the vibration diaphragm to serve as a lower electrode plate of the capacitor. The terms “upper” and “lower” are only used to distinguish the relative position between the two electrode plates but not to represent their final position relation in the speaker unit. When the moving-coil speaker works, the capacitance of the capacitor changes to feed back vibration displacement of the vibration diaphragm, thus improving the acoustic performance of the speaker by monitoring the vibration displacement of the vibration diaphragm of the speaker unit.
Since the lower electrode plate of the capacitor disposed on the DOME needs to be led out by a lead to acquire capacitance data of the electrode plates, and vibrates when the DOME and the vibration diaphragm vibrate together, the lead on the lower electrode plate of the capacitor is easy to fracture due to vibration. Consequently, the capacitance data may not be acquired. The vibration displacement of the vibration diaphragm may not be monitored. The reliability of capacitance data acquisition is low.